Web Application Testing
anthropics/skills
Tests local web applications with Python Playwright scripts, checking frontend behavior, capturing screenshots and reading browser console logs.
Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction.
Install Port Engine Changes
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changes --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/port-engine-changes .claude/skills/port-engine-changes && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .claude/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changesType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changes --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/port-engine-changes .agents/skills/port-engine-changes && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .agents/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changes --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/port-engine-changes .cursor/skills/port-engine-changes && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .cursor/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/nordstjernen-web/northstar-browser.git --path .agents/skills/port-engine-changes--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changes --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/port-engine-changes .gemini/skills/port-engine-changes && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .gemini/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changesInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/port-engine-changes .github/skills/port-engine-changes && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .github/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install nordstjernen-web/northstar-browser port-engine-changes --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/port-engine-changes .opencode/skills/port-engine-changes && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "port-engine-changes" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/port-engine-changes into .opencode/skills/port-engine-changes/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "port-engine-changes", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
port-engine-changes- GitHub stars
- 127
- Token cost
- ~1.1k tokens
- SKILL.md length
- 625 words
- Files
- 2
- Skills in repo
- 5
- Repo updated
- First seen
- Licence
- GPL-3.0
At a glance
Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction.
- Works in 3 steps: Compare commit subjects only to… → Confirm presence or absence by searching… → Discard anything the destination…
- Cherry-picks where the two trees share most engine sources but differ in features
- SKILL.md covers Establish what is already there, Check applicability before…, Expect edition-specific breakage and Verify in the destination, not…, plus 2 more sections
- Calls git
What it does
Port Engine Changes is an agent skill from nordstjernen-web/northstar-browser. Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction. Use for backports, forward-ports, and cherry-picks where the two trees share most engine sources but differ in features, helpers, or vendored dependencies.
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files (for example `agents/openai.yaml`).
It sits in Testing & QA. The repository describes itself as: Northstar web browser, Open Source License: GPL v3. Northstar web browser is a real web browser, not based on Firefox or Chrome. The licence is GPL-3.0.
When your agent uses it
- Cherry-picks where the two trees share most engine sources but differ in features
- Vendored dependencies
Example prompts
- “/port-engine-changes”
Workflow steps
3 steps, taken from the first numbered list in SKILL.md.
- Compare commit subjects only to shortlist candidates. The same fix often lands in both trees under different wording, so a subject that…
- Confirm presence or absence by searching the destination for the code the change introduces — a new function, field, or predicate — not by…
- Discard anything the destination excludes by policy: features the scope forbids, dependencies it vendors differently, and modules it does…
What it can do on your machine
Read from SKILL.md and the folder at commit 98475ea. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
git
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Port Engine Changes loads about 1.1k tokens when it runs. Until then it costs about 74 tokens; SKILL.md has 625 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from nordstjernen-web/northstar-browser at commit 98475ea, republished under its GPL-3.0 licence (© nordstjernen-web). 625 words, ~1,127 tokens.
Download SKILL.mdSave it as
.claude/skills/port-engine-changes/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- port-engine-changes
- description
- Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction. Use for backports, forward-ports, and cherry-picks where the two trees share most engine sources but differ in features, helpers, or vendored dependencies.
Port Engine Changes Between Editions
Read the repository instructions of the destination tree first. Preserve unrelated changes. The source commit is evidence, not authority: it was verified against a different tree.
Establish what is already there
- Compare commit subjects only to shortlist candidates. The same fix often lands in both trees under different wording, so a subject that looks absent may already be present.
- Confirm presence or absence by searching the destination for the code the change introduces — a new function, field, or predicate — not by trusting the log.
- Discard anything the destination excludes by policy: features the scope forbids, dependencies it vendors differently, and modules it does not build.
Check applicability before committing to it
Generate a patch from the source commit and test it against the destination:
git format-patch -1 <commit> --stdout -- src/ > /tmp/port.patch
git apply --check /tmp/port.patchPrefer this to adding a remote for the other tree: it keeps the histories separate and makes divergence visible immediately. A patch that does not apply is a signal to port by hand, not to force it.
Expect edition-specific breakage
A change that compiles in one tree can fail in the other because the destination lacks a helper the source takes for granted, declares it later in the file, or gives it a different signature. Compilers report this as an implicit declaration followed by a conflicting redeclaration, and the symbol then fails to link.
Before porting, resolve every function the change calls against the destination. When a helper is missing, either lift it out of the destination's own equivalent code or express the call through primitives the destination already has. Do not copy a helper that duplicates one the destination spells differently.
Verify in the destination, not the source
Compiling the changed translation units alone is not sufficient: it misses missing declarations in other units, link errors, and header drift. Build the whole destination tree.
Work in a clean worktree checked out at the destination's published head so a shared or mid-edit working tree cannot contaminate the result:
git worktree add --detach <tmp> origin/mainThen exercise the behavior the change is supposed to alter, and confirm it differs from the unported build in the direction the source commit claims. A port that builds but changes nothing observable has not been verified.
Show full SKILL.md (258 more words)Show less
Record the origin
Name the source commit in a Ported-From: <owner>/<repo>@<full sha> trailer, taking the sha from git rev-parse rather than typing it, and describe the behavior in the destination's own terms. When the source carries a Security-Fix: slug, keep it; when it is a security fix without one, give the port a new slug. Both trailers belong in the final trailer block next to Co-Authored-By, where git interpret-trailers finds them. Do not copy a message that refers to code, tests, or scores that do not exist in the destination.
Northstar context
Northstar is the purist GPL edition of Nordstjernen; the engine sources are largely shared, but code crosses into Northstar only under the provenance rules in AGENTS.md: from Nordstjernen and Southstar only the copyright holder's own commits, never an external contributor's without their written GPL license. Check the author of every source commit before checking applicability, and stop if it fails. A Claude-authored commit can still build on code an outside contributor wrote; port only the parts that stand without it. Both trees are edited continuously, so re-read the destination head immediately before porting.
Differences that break ports in practice: Northstar consumes quickjs-ng as an upstream meson subproject and carries no in-tree engine fork, so changes that patch a vendored JavaScript engine do not apply; the features the repository instructions exclude from this edition are absent here; and helper availability in src/js.c differs between the trees even where the surrounding code matches.
Push only to the destination's own remote. Never push one edition's history to the other's.
© nordstjernen-web, GPL-3.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file in .agents/skills/port-engine-changes of nordstjernen-web/northstar-browser.
- SKILL.md
- agents/openai.yaml
Open the folder on GitHubat commit 98475ea
Compare with similar skills
Port Engine Changes next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Port Engine Changes this skillnordstjernen-web/northstar-browser | 127 | — | ~1.1k | Automated safety check: Pass | GPL-3.0 | |
| Web Application Testinganthropics/skills | 180k | 51 repos | ~966 | Automated safety check: Pass | Apache-2.0 | |
| Diagnosing Bugsfossasia/eventyay-interpretation | 1.6k | 32 repos | ~2.1k | Automated safety check: Pass | Apache-2.0 | |
| TDDpietheinstrengholt/rssmonster | 564 | 30 repos | ~906 | Automated safety check: Pass | MIT | |
| TDD WorkflowhellangleZ/burn-in-cceverywhere-ralph | 112 | 11 repos | ~2.4k | Automated safety check: Pass | None | |
| TDDsanity-io/sanity | 6.4k | 20 repos | ~1k | Automated safety check: Pass | MIT |
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Categories
Questions about Port Engine Changes
What does Port Engine Changes do?
Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction. Port Engine Changes is an agent skill from nordstjernen-web/northstar-browser. Port a browser-engine change between sibling editions or long-lived branches of the same codebase, in either direction.
When should I use Port Engine Changes?
Port Engine Changes fits situations like: cherry-picks where the two trees share most engine sources but differ in features; vendored dependencies.
How do I install Port Engine Changes in Claude Code?
Run `npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a claude-code`. Or copy the skill folder (.agents/skills/port-engine-changes in nordstjernen-web/northstar-browser) into .claude/skills/port-engine-changes in your project. Claude Code loads it when a task matches its description.
How do I install Port Engine Changes in Codex?
Run `npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a codex`. Or copy the skill folder (.agents/skills/port-engine-changes in nordstjernen-web/northstar-browser) into .agents/skills/port-engine-changes in your project. Codex loads it when a task matches its description.
Can I use Port Engine Changes in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add nordstjernen-web/northstar-browser --skill port-engine-changes -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/port-engine-changes, .gemini/skills/port-engine-changes, .github/skills/port-engine-changes and .opencode/skills/port-engine-changes in your project.
What does Port Engine Changes need to run?
Going by SKILL.md and its folder, Port Engine Changes needs the command-line tools its instructions call (git).
Does Port Engine Changes access the network?
SKILL.md contains no URLs. Its commands use git, which can reach the network depending on how they are called. This is read from the text; nothing was executed.
Is Port Engine Changes safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Port Engine Changes use?
Port Engine Changes is published under the GPL-3.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Port Engine Changes use?
About 1.1k tokens (SKILL.md is roughly 4.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Port Engine Changes?
Skills that share tags, products or a category with Port Engine Changes: Web Application Testing (anthropics/skills, 180k stars), Diagnosing Bugs (fossasia/eventyay-interpretation, 1.6k stars), TDD (pietheinstrengholt/rssmonster, 564 stars) and TDD Workflow (hellangleZ/burn-in-cceverywhere-ralph, 112 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Port Engine Changes?
nordstjernen-web (a GitHub organization) maintains it in nordstjernen-web/northstar-browser, which has 127 GitHub stars. The repository holds 5 skills in this directory. The repository was last updated on October 10, 2026.
Source: nordstjernen-web/northstar-browser on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.